MULTIOBJECTIVE MATERIAL ARCHITECTURE OPTIMIZATION OF PULTRUDED FRP I-BEAMS

This paper presents the application of micro/macromechanics models and optimization techniques for the optimum design of pultruded glass fib er-reinforced plastic composite I-beams with respect to material archi tecture: fiber orientations and fiber percentages. The beams are subje cted to transverse loading, and beam deflection, buckling resistance a nd material failure are considered as multiple objectives (criteria) i n the optimization process. Assuming a symmetrical laminated structure for the pultruded sections, experimentally verified micro/macromechan ics models are used to predict ply properties, beam member response an d ply strains and stresses. The Tsai-Hill failure criterion is used to determine first-ply-failure loads. Considering the coupling of latera l and distortional buckling, a stability Rayleigh-Ritz solution is use d to evaluate the critical buckling loads for pultruded I-beams, and t he results are verified with finite element analyses. A multiobjective design optimization formulation combined with a global approximation technique is proposed to optimize beam fiber architecture, which can g reatly enhance the load carrying capacity of a section. The optimizati on procedure presented in this paper can serve as a practical tool to improve the performance of existing fiber-reinforced plastic without c hanging the current geometries. Copyright (C) 1996 Elsevier Science Lt d.